Geochemical and transport properties of dissolved organic carbon in a clay‐rich aquitard
Bibliographic record
Abstract
The properties and controls on the diffusive transport of dissolved organic carbon (DOC) in a thick clay‐rich till aquitard were investigated. DOC was measured in 14 piezometers ranging in depth from 1.2 to 43 m below ground (BG). The DOC data showed a decrease in concentration with depth from 168 mg/L in the surficial, fractured, and oxidized zone (1.2 m BG) through the thick underlying unoxidized and nonfractured aquitard, reaching minimum values of between 12 and 16 mg/L below 15 m. Flow field‐field flow fractionation analyses showed that the DOC was uniform with respect to hydrodynamic size (2.5 nm), molecular weight (approximately 900 Da), and aqueous diffusion coefficient (1.9 × 10−10 m2/s). Specific UV aborbance (UV/TOC) varied with depth but was significantly lower than surface water DOC. Results of batch experiments showed that DOC exhibited negligible sorption (i.e., kd = 1.1 × 10−3 mL/g) to the aquitard matrix. Double‐reservoir diffusion tests showed that DOC diffuses through this clay‐rich media. Results of best fit numerical modeling of the diffusion cell data yielded an effective diffusion coefficient of 9 × 10−11 m2/s for the DOC and suggested that the effective porosity for the DOC may be approximated by the total porosity. Pore aperture measurements on core samples and the results of the diffusion cell experiments revealed that straining of DOC by the aquitard matrix does not occur. Overall, our results suggested that DOC can diffuse through clay‐rich aquitards in a similar manner to conservative inorganic solutes.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".